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What are “beta-blockers”?
As beta adrenergic receptor antagonists, they diminish the effects of epinephrine (adrenaline) and other stress hormones. Invented by Sir James W. Black in the late 1950s, Propranolol was the first clinically useful beta-blocker; it revolutionized the medical management of angina pectoris and is considered to be one of the most important contributions to clinical medicine and pharmacology of the 20th century. Beta-blockers may also be referred to as beta-adrenergic blocking agents, beta-adrenergic antagonists, or beta antagonists.
Although beta-blockers were once contraindicated in congestive heart failure, as they have the potential to worsen the condition, studies in the late 1990s showed their positive effects on morbidity and mortality in congestive heart failure. Bisoprolol, carvedilol and sustained-release metoprolol are specifically indicated as adjuncts to standard ACE inhibitor and diuretic therapy in congestive heart failure.
Beta-blockers are primarily known for their reductive effect on heart rate, although this is not the only mechanism of action of importance in congestive heart failure. Beta-blockers, in addition to their sympatholytic B1 activity in the heart, influence the renin/angiotensin system at the kidneys. Beta-blockers cause a decrease in renin secretion, which in turn reduce the heart oxygen demand by lowering extracellular volume and increasing the oxygen carrying capacity of blood. Beta-blockers sympatholytic activity reduce heart rate, thereby increasing the ejection fraction of the heart despite an initial reduction in ejection fraction.
Trials have shown that beta-blockers reduce the absolute risk of death by 4.5% over a 13 month period. As well as reducing the risk of mortality, the number of hospital visits and hospitalizations were also reduced in the trials.
Since they promote a lower heart rate and reduce tremor, beta-blockers have been used by some Olympic marksmen to enhance performance, though beta-blockers are banned by the International Olympic Committee (IOC). Although they have no recognisable benefit to most sports, it is acknowledged that they are beneficial to sports such as archery and shooting. A recent, high-profile transgression took place in the 2008 Summer Olympics, where 50 metre pistol silver medallist and 10 metre air pistol bronze medallist Kim Jong-su tested positive for propranolol and was stripped of his medal.